It is known that when electric cables, telecommunication cables, flexible hoses or elongated elements in general, are laid underwater, they are laid in appropriate trenches to avoid possible damage. On account of the sea depth, which is sometimes relevant, and of the consequent difficulty for the operators to work at such a depth, the laying of the elongated element is carried out by means of laying machines, remotely controlled by the tender ship, which, while progressively advancing on the sea bed, dig the trench and deposit the elongated element therein.
More particularly, said machines lift the elongated element, cause it to slide along ways thereon, and then lay it on the trench bottom. Because of the high friction generated between the elongated element and the sliding means or ways, the portion of the elongated element situated downstream of the laying machine is subjected to a tension greater than that applied to the portion situated upstream, so that a surplus of elongated element begins to accumulate upstream of the laying machine.
On account of the considerable length of the elongated elements, the accumulated surplus can become detrimental in a short time. In fact, the elongated elements may bend at short bending radii, which may impair them, or even may be trapped under the laying machine, with a high risk of damage to the elements and/or to the laying machine.
To eliminate this disadvantage, some laying machines are provided in their front part with a mechanical moving arm, terminating with a guide into which the elongated element passes. When a surplus of the elongated element accumulates upstream of the laying machine, the mechanical arm is raised, lifting the elongated element and avoiding situations of risk for the element and/or for the laying machine.
Said machines, however, solve the problem only temporarily, since they are unable to transfer the accumulated surplus from upstream to downstream and, therefore, to avoid accumulation during the progressive advancement of the machine.